Stage 2 · Understanding the illness
Other infections the same tick can carry
Other infections the same tick can carry, and what each test can and cannot settle.
Stage 2 · Understanding the illness
Other infections the same tick can carry
A single tick can carry several organisms and transmit them in one bite. They cause different illnesses, respond to different treatments, and some, such as Babesia, are not treated by the antibiotics used for Lyme — so they are worth asking about.
Review statePending clinical review
Which coinfections travel together, and the presentation described for each. A clinically-informed reviewer has not yet signed this off, and it stays marked until one does.
Printed as a one-page sheet: the coverage table and what to ask. The full guide is at lymehq.com/coinfections.
It is one of the first questions worth asking. A single tick can carry several organisms and pass them on in one bite; they cause different illnesses and respond to different treatments. Babesia is a parasite rather than a bacterium, and the antibiotics used for Lyme do not touch it. Testing for coinfections is separate from Lyme testing and is often not ordered unless someone asks. The matrix below turns “was I tested for everything?” into a list of gaps you can take to a clinician.
Test quality varies by organism, so a negative does not mean the same thing everywhere. Serology for Babesia and Bartonella has known limits, which makes a negative there weaker evidence than a negative Lyme test. That is why the matrix asks which assay was used and how it was validated beside every result, and why what it hands back is a list of gaps rather than an answer about you.
What has and hasn’t been tested
No account. Tap what you know — nothing is saved, and nothing is sent anywhere. Print it if you want to keep it or hand it over.
The panel is the illnesses this site’s treatment reference holds — not every organism a tick can carry. If a clinician names one that isn’t listed here, that is a gap too.
- Lyme DiseaseBorrelia burgdorferi (and B. mayonii)tap Yes · No · ?ask which assay, and how it was validatedNot answered.
- BabesiosisBabesia microti, B. duncanitap Yes · No · ?ask which assay, and how it was validatedNot answered.
- Bartonella — not established as tick-borneBartonella henselae, B. quintanatap Yes · No · ?ask which assay, and how it was validatedNot answered.
- Ehrlichiosis / AnaplasmosisEhrlichia chaffeensis; Anaplasma phagocytophilumMore than one organism on this row — a test for one is not a test for the other. Worth asking which was run.tap Yes · No · ?ask which assay, and how it was validatedNot answered.
- Alpha-gal SyndromeLone Star tick–induced (galactose-α-1,3-galactose allergy)tap Yes · No · ?ask which assay, and how it was validatedNot answered.
- Rocky Mountain Spotted FeverRickettsia rickettsiitap Yes · No · ?ask which assay, and how it was validatedNot answered.
- Powassan VirusPowassan virus (flavivirus)tap Yes · No · ?ask which assay, and how it was validatedNot answered.
- TularemiaFrancisella tularensistap Yes · No · ?ask which assay, and how it was validatedNot answered.
- Lyme Disease — not answered yet
- Babesiosis — not answered yet
- Bartonella — not established as tick-borne — not answered yet
- Ehrlichiosis / Anaplasmosis — not answered yet
- Alpha-gal Syndrome — not answered yet
- Rocky Mountain Spotted Fever — not answered yet
- Powassan Virus — not answered yet
- Tularemia — not answered yet
A gap is an organism with no test recorded, a result that has not settled it, or a test whose assay weakens it. It is never a likelihood that you have anything.
The empiric-treatment gap
Doxycycline is the antibiotic usually reached for first when Lyme is suspected, and part of why is that it covers anaplasmosis and ehrlichiosis as well. It does nothing for Babesia, which is a parasite rather than a bacterium. That is the gap: a case treated correctly for Lyme can leave a second infection untouched. Organisms are named here and nothing else — how much and how long is a clinician’s decision and is not on this site.
- Lyme Disease
- Covered — it is the first-line drug
- Babesiosis
- Not covered — this one is treated with something else
- Ehrlichiosis / Anaplasmosis
- Covered — it is the first-line drug
- Rocky Mountain Spotted Fever
- Covered — it is the first-line drug
- Powassan Virus
- Not covered — this one isn’t treated with an antibiotic
- Tularemia
- Named, but as an alternative
Read row by row from the same treatment reference this site renders at treatment protocols, not typed into this page.
Which travel together
Pending review · no cells yetThe symptom-overlap grid has a place on this page and no cells in it. Which symptoms are commonly reported with which infection is editorial judgement rather than a published table, so no grid is shown until a clinically-informed reviewer signs off cells that can be sourced. It is not filled in by guesswork in the meantime.
What symptoms can do in the meantime: very little on their own — which is why the matrix above asks about tests rather than about how you feel.
Why they travel together
Ticks feed on several hosts across their life cycle, and pick up whatever each host is carrying. By the time one reaches a person it may be carrying more than one organism, and a single bite can pass on more than one. Nothing about a bite tells you which — the tick looks the same either way.
Bartonella is spread to people mainly by fleas, body lice and sand flies, and by scratches from flea-infested cats. CDC states there is no evidence that ticks spread Bartonella to people. It has been found in ticks, and one laboratory study showed a tick passing it to an animal; whether that happens in nature is not known. Some clinicians who treat persistent illness after a tick bite consider it anyway — a proposed route of infection, not an established one.
This matters because they are not variations of one illness. A bacterium and a parasite are different problems with different treatments, and something that clears one may not touch the other.
It is also why a single negative test is weak evidence. Testing for coinfections is separate from Lyme testing and is often not ordered unless someone asks — the testing guide covers what to ask for and why timing changes what a result means.
What a tick carries is not just Lyme
Three of the ticks that bite people in the United States, and what CDC lists each one as transmitting.
What CDC lists each species as transmitting — not what any one tick is carrying, and not a diagnosis.
US Centers for Disease Control and Prevention, Where Ticks Live, read 10 October 2026: what CDC lists each species as transmitting. Nothing on this drawing is a measured quantity.
What each one is
How each differs from Lyme, and what that difference means in practice. Treatment approaches for each are in treatment protocols.
Babesiosis
Babesia microti, B. duncaniBabesia is a malaria-like parasite that lives in red blood cells, so it needs antiparasitic treatment — not the antibiotics used for Lyme. Symptoms like night sweats, air hunger, and drenching chills are worth flagging to your provider, since Babesia is easy to miss and often travels with Lyme. How atovaquone (Mepron) is taken affects how well it is absorbed, so follow your prescriber's instructions.
Alongside LymeBabesia infects red blood cells. It is a parasite, not a bacterium, and CDC describes babesiosis as treated with different medications from Lyme — so a Lyme course does not treat it.
Your provider determines your treatment based on your presentation, history, and current guidelines.
Bartonella — not established as tick-borne
Bartonella henselae, B. quintanaBartonella is spread to people mainly by fleas, body lice and sand flies, and by scratches from flea-infested cats. Those infections are real and are treated with antibiotics chosen by a clinician. CDC states there is no evidence that ticks spread Bartonella to people. If you have had contact with cats, fleas or lice, that exposure is the useful thing to mention.
Alongside LymeBartonella found in a person who also has Lyme is not evidence that the same tick passed on both.
Your provider determines testing and treatment based on your exposures, presentation and history.
Ehrlichiosis / Anaplasmosis
Ehrlichia chaffeensis; Anaplasma phagocytophilumThese infections are treated with doxycycline. Because they can escalate fast, providers frequently start treatment based on symptoms and exposure rather than waiting for test confirmation.
Alongside LymeAnaplasmosis is spread by the blacklegged tick, the same tick that carries Lyme; ehrlichiosis by the lone star tick and the blacklegged tick (CDC). Doxycycline covers Lyme and both of these infections, which is part of why it's preferred for early empiric treatment.
Your provider determines your treatment based on your presentation, history, and current guidelines.
Rocky Mountain Spotted Fever
Rickettsia rickettsiiRMSF is serious and moves fast — fever, headache, and a rash that often starts on wrists and ankles. If a provider suspects it, they will start doxycycline right away rather than waiting for tests, because early treatment is what prevents serious harm. Seek care urgently for these symptoms after a tick bite.
RMSF requires urgent medical care — this reference does not replace emergency evaluation.
Powassan Virus
Powassan virus (flavivirus)Powassan is rare but serious, and because it's a virus, there's no antibiotic or specific cure — doctors treat the symptoms and support the body, especially if the brain is affected. This is one where prevention matters most: it can transmit very quickly after a tick attaches, so prompt tick removal and bite prevention are key.
Suspected Powassan requires urgent medical evaluation; care is supportive and individualized.
Tularemia
Francisella tularensisTularemia is uncommon, and it is treated with different antibiotics from Lyme. It can come from tick bites as well as contact with infected animals. Prompt treatment matters, so tell your provider about any tick or animal exposure.
Your provider determines your treatment based on your presentation, history, and current guidelines.
And from the Lyme side
The blacklegged tick that carries Lyme can also carry Babesia and Anaplasma, and one bite can pass on more than one. CDC states there is no evidence that ticks spread Bartonella to people. Some coinfections, such as Babesia, are not treated by the antibiotics used for Lyme — CDC describes babesiosis as a parasitic disease treated with different medications — so they are worth asking about.
How common each coinfection is alongside Lyme in a given county — surveillance for most of them is thin, and the counting rules differ from the ones Lyme is counted under. Whether treating a coinfection resolves symptoms that persisted after Lyme treatment: that is not settled, and this page does not adjudicate it. Whether these organisms interact inside a person the way they do in a laboratory. This page structures those questions; it does not answer them.
- “Here is what I have been tested for and what I haven’t. Which gaps matter for my picture?”
- “For the ones you’d test, which assay — and is it FDA-cleared or laboratory-developed?”
- “If a coinfection were present, what would you expect to see that we haven’t looked at?”